Direct-current tracing control high-power photovoltaic grid-connected inverter

Abstract

The invention discloses a high-efficiency low-harmonic distortion rate high-power photovoltaic grid-connected inverter (100). The photovoltaic grid-connected inverter comprises a high frequency inverter (10), a series-connected resonance circuit (20), a fast incontrollable rectifier (30) and a power frequency inverter (40), wherein the high frequency inverter (10) is used for transforming the voltage of a photovoltaic array into impulse level; the series-connected resonance circuit (20) transforms the impulse level into sinusoidal voltage and current; the high frequency inverter (10) outputs a level impulse according to direct-current tracing control, so that the resonant amplitude of the series-connected resonance circuit (20) can be continuously adjusted, and traces the change of rectified grid voltage; the incontrollable rectifier (30) transforms the sinusoidal voltage with different amplitude values into direct-current voltage which traces the change of the rectified grid voltage;and the power frequency inverter (40) switches to trigger when the grid voltage crosses a zero point and is used for tracing the change of the grid voltage with output voltage. The inverter can be applied to the large-scale high voltage grid connection of photovoltaic electric power generating systems.

Description

technical field [0001] The invention relates to an inverter, in particular to a photovoltaic grid-connected inverter with high efficiency, low harmonic distortion rate, high power and DC tracking control. Background technique [0002] Grid-connected photovoltaic power generation technology is an important direction developed in the field of new energy in the past ten years. It directly connects the photovoltaic power generation system with the grid, eliminating the need for large, expensive, and difficult-to-maintain batteries. To achieve grid-connected operation, photovoltaic grid-connected inverters must meet two basic requirements: (1) The output voltage is the same frequency, phase, and amplitude as the grid voltage; (2) The power factor is -1, that is, the output The current must have the same frequency and phase as the grid voltage. The grid-connected inverter does not need a battery, and the output is directly connected to the grid. In order not to cause harmonic pol...

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Problems solved by technology

According to the "Renewable Energy Medium and Long-Term Development Plan" issued by my country in September 2007, in 2020, the cumulative installed capacity of solar power generation equipment in my country will reach 2000MW. Great damage to the stability of the power grid is likely to cause the failure of the entire power grid

The way of pulse width modulation will inevitably bring harmonic distortion, which cannot be eliminated. To further improve the efficiency of photovoltaic grid-connected inverters, reduce or even eliminate the harmonic distortion rate during grid-connection is a must for large-scale photovoltaic array grid-connection. key issues

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